I love the tangy sharpness that lemon curd adds to a classic treacle tart. The recipe uses light treacle, generally known as golden syrup, a common British sweetener made from evaporating sugar cane juice until it’s thick and syrupy. You can find golden syrup at British specialty shops or online; Or you can substitute corn syrup or maple syrup. Do make sure the pastry base is well cooked before you add the curd or it will get soggy, and take the tart out of the oven while it still has a slight wobble. It will firm up more as it cools.
First make the sweet pastry. Place the butter and sugar in a food processor and process until just combined. Add the egg and process for 30 seconds.
Tip in the flour and process for a few seconds until the dough just comes together. (Do not overprocess or it will become tough.) Add a little ice-cold water (around a tablespoon) if the dough seems too dry.
Knead the dough lightly on a floured surface and shape into a flat disc. Wrap in plastic wrap and chill for 30 minutes before rolling out.
To make the tart, roll out the pastry on a lightly floured surface to a large round the thickness of ⅛ inch. Use to line a loose-bottomed tart pan (9–10 inches), leaving some excess pastry overhanging the rim. Chill for 30 minutes. Meanwhile, preheat the oven to 375°F.
Line the pastry case with parchment paper and ceramic baking beans or uncooked rice and bake “blind” for 15–20 minutes until the base is cooked through. Carefully remove the beans and paper and allow the pastry to cool a little. While still warm, cut off the excess pastry to level with the rim of the pan. Lower the oven setting to 300°F.
To make the filling, gently heat the golden syrup in a saucepan along with the butter. (Be careful not to boil this—just allow the butter to melt.)
When the butter has melted, stir in the cream, lemon zest and juice, and breadcrumbs, then add the egg yolks. Mix well.
Spread the lemon curd over the base of the baked pastry case, then pour in the filling.
Bake for 30–40 minutes until the top has just set but the center is slightly wobbly when you shake the pan gently. It should still feel slightly soft in the center.
Let the tart cool completely before slicing and serving.
HOW TO PREVENT PASTRY SHRINKAGE
Pastry tends to shrink when cooked—that’s why leaving it overhanging the pan and trimming after baking is a good idea. Use a very sharp knife and you will be left with a lovely neat edge.